Feed-forward and its role in conditional linear optical quantum dynamics

*Physical Review A* **73**, 034301 (2006)

It is well known that one can create nonlinear optical quantum gates probabilistically using only single photon sources, linear optical elements and photon-number resolving detectors. These gates are heralded but operate with probabilities much less than one. There is currently a large gap between the performance of these known circuits and the established upper bounds on their success probabilities. One possibility for increasing the probability of success of such gates is feed-forward, where one attempts to correct certain failure events that occurred in the gates operation. In this brief report we examine the role of feed-forward in improving the success probability of linear optical gates and the cost in resources.